Modified UI model objects to be backed merely by IDs of the core model objects.

Change-Id: I4ca81fb1c877ee4ce4209d405fd8c6645c8f5d20
diff --git a/web/gui/src/main/java/org/onosproject/ui/impl/topo/model/ModelCache.java b/web/gui/src/main/java/org/onosproject/ui/impl/topo/model/ModelCache.java
index 2377499..12d75f3 100644
--- a/web/gui/src/main/java/org/onosproject/ui/impl/topo/model/ModelCache.java
+++ b/web/gui/src/main/java/org/onosproject/ui/impl/topo/model/ModelCache.java
@@ -85,13 +85,14 @@
 
     private final ServiceBundle services;
     private final EventDispatcher dispatcher;
-    private final UiTopology uiTopology = new UiTopology();
+    private final UiTopology uiTopology;
 
     private Topo2Jsonifier t2json;
 
     ModelCache(ServiceBundle services, EventDispatcher eventDispatcher) {
         this.services = services;
         this.dispatcher = eventDispatcher;
+        uiTopology = new UiTopology(services);
     }
 
     @Override